What is the reason for the fuel pump continuously making noise when the key is turned on?
2 Answers
The reasons for the fuel pump continuously making noise when the key is turned on are as follows: Dirty fuel filter: The car's fuel filter is equipped with a pressure relief valve. When the pressure exceeds the specified value (4 bar for 1.6L engines and 6 bar for 1.8T engines), its purpose is to protect the fuel pump from burning out. A puffing whistle sound occurs during pressure relief, and occasionally hearing this sound is normal pressure relief operation. If this persists, it is likely due to a dirty filter element causing increased pressure, which leads to the pressure relief valve opening to release pressure. In this case, the fuel filter needs to be replaced. Using low-quality gasoline: Using low-quality gasoline, which generally contains various impurities, foreign objects, and additives. Although the bottom of the fuel pump can filter out most impurities, those that are not filtered enter the fuel pump motor, accelerating wear.
The last time I encountered this situation was with my friend's old Focus, which had run 80,000 kilometers. After inserting the key, the fuel pump kept buzzing non-stop. Normally, it does make some noise when working, but continuous buzzing is not right. The prime suspect is that the fuel pump is about to retire, with worn brushes or stuck bearings inside, struggling to maintain speed and making a rattling noise like a broken electric fan. It could also be that the fuel pump filter screen is clogged with impurities in the tank, making it hard to suck fuel and causing it to howl. Another possibility is that the relay is stuck in the on position and won't release, like holding down a doorbell without letting go. Get it checked ASAP—my friend delayed for a few days and ended up stranded on the road, costing over 300 for a tow truck.
